2 The procedure
2.1.1 Non-surgical reduction of the myocardial septum is used to treat outflow tract obstruction in patients with hypertrophic obstructive cardiomyopathy (HOCM). Patients with HOCM have abnormally thickened heart muscle, which narrows the outflow tract from the left ventricle, often causing chest pain, breathlessness, palpitations and fainting spells. There is an increased risk of sudden death from heart attacks or abnormal heart rhythms.
2.1.2 Most patients with HOCM are treated with medication. More invasive treatments may be considered in patients who still get symptoms despite drug treatment. The standard surgical treatment is ventricular septal myotomy-myectomy, using an open surgical technique that requires cardiopulmonary bypass.
2.2.1 Non-surgical reduction of the myocardial septum does not require open chest surgery or cardiopulmonary bypass. It involves inserting a catheter into the femoral artery and passing it up into the heart under X-ray control. Alcohol is injected into an artery that supplies blood to the septum. This destroys a part of the muscle in the septum, which then becomes thinner.
2.3.1 The studies showed that non-surgical reduction of the myocardial septum is efficacious in the short term. In three non-randomised studies, the mean reduction in gradient across the left ventricular outflow tract (LVOT) ranged from 22 mmHg to 42 mmHg, and compared favourably to the mean reduction in LVOT gradient for open surgery. The studies also reported reduced numbers of patients suffering from severe breathlessness and fainting spells after treatment. There is, however, a lack of long-term follow-up. For more details, refer to the 'Sources of evidence' section.
2.3.2 The Specialist Advisors considered the procedure to be an established alternative to surgical relief of outflow tract obstruction in patients with HOCM.
2.4.1 In the studies, the most commonly reported complication was the need for patients to have a pacemaker implanted permanently because of complete heart block following the procedure. In one non-randomised study of 41 patients, 9 patients (22%) required a permanent pacemaker. The same study reported one procedure-related death. For more details, refer to the 'Sources of evidence' section.
2.4.2 The Specialist Advisors cited a 10% risk of complete heart block, requiring patients to have a permanent pacemaker implanted after having the procedure. The Advisors considered the procedure to be safe when performed by experienced operators in specialist units with an established interest in HOCM.